Bicycle sprocket

ABSTRACT

A bicycle sprocket comprises sprocket teeth. The sprocket teeth include at least one first tooth and at least one second tooth. The at least one first tooth has a first radial-tooth height. The at least one first tooth has an axial center plane in an axial direction parallel to the rotational center axis. The at least one second tooth is adjacent to the first tooth and disposed on a downstream side in a rotational driving direction of the bicycle sprocket. The at least one second tooth has a second radial-tooth height. The first radial-tooth height is greater than the second radial-tooth height. The at least one first tooth includes a tooth tip having an axial center plane in the axial direction. The axial center plane of the tooth tip is offset from the axial center plane of the first tooth in an axial direction.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation application of the U.S. patentapplication Ser. No. 14/283,165 filed May 20, 2014. The contents of thisapplication are incorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a bicycle sprocket.

Discussion of the Background

Bicycling is becoming an increasingly more popular form of recreation aswell as a means of transportation. Moreover, bicycling has become a verypopular competitive sport for both amateurs and professionals. Whetherthe bicycle is used for recreation, transportation or competition, thebicycle industry is constantly improving the various components of thebicycle. One component that has been recently redesigned is a bicyclesprocket.

Most bicycles have a drive train that uses the bicycle sprocket totransmit the pedaling action from the rider to a bicycle wheel through abicycle chain. A front sprocket and a rear sprocket have been known asthe bicycle sprocket. The bicycle sprocket generally includes aplurality of teeth to engage with the bicycle chain.

SUMMARY OF THE INVENTION

In accordance with an aspect of the present invention, a bicyclesprocket has a rotational center axis. The bicycle sprocket comprisessprocket teeth. The sprocket teeth include at least one first tooth andat least one second tooth. The at least one first tooth is configured toengage with outer link plates of a bicycle chain and has a firstradial-tooth height. The at least one first tooth has a firstchain-engaging axial width which is smaller than a first distancedefined between opposed outer link plates of the bicycle chain and whichis larger than a second distance defined between opposed inner linkplates of the bicycle chain. The at least one first tooth has an axialcenter plane in an axial direction parallel to the rotational centeraxis. The at least one second tooth is adjacent to the first tooth anddisposed on a downstream side in a rotational driving direction of thebicycle sprocket. The at least one second tooth is configured to engagewith inner link plates of the bicycle chain. The at least one secondtooth has a second radial-tooth height. The first radial-tooth height isgreater than the second radial-tooth height. The at least one firsttooth includes a tooth tip having an axial center plane in the axialdirection. The axial center plane of the tooth tip is offset from theaxial center plane of the first tooth in the axial direction.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings, wherein:

FIG. 1 is an elevational view of a bicycle sprocket in accordance with afirst embodiment;

FIG. 2 is an enlarged elevational view of the bicycle sprocketillustrated in FIG. 1;

FIG. 3 is a partial perspective view of the bicycle sprocket illustratedin FIG. 1;

FIG. 4 is a cross-sectional view of the bicycle sprocket taken alongline IV-IV of FIG. 2;

FIG. 5 is a cross-sectional view of the bicycle sprocket taken alongline V-V of FIG. 2;

FIG. 6 is a cross-sectional view of the bicycle sprocket taken alongline VI-VI of FIG. 2;

FIG. 7 is an enlarged elevational view of the bicycle sprocketillustrated in FIG. 1 for explaining positional relationship between thebicycle sprocket and a bicycle chain;

FIG. 8 is an enlarged elevational view of a bicycle sprocket inaccordance with a second embodiment;

FIG. 9 is a cross-sectional view of the bicycle sprocket illustrated inFIG. 8;

FIG. 10 is an enlarged elevational view of a bicycle sprocket inaccordance with a third embodiment;

FIG. 11 is a cross-sectional view of the bicycle sprocket taken alongline XI-XI of FIG. 10;

FIG. 12 is a cross-sectional view of the bicycle sprocket taken alongline XII-XII of FIG. 10;

FIG. 13 is a cross-sectional view of a bicycle sprocket in accordancewith a fourth embodiment;

FIG. 14 is an enlarged elevational view of a bicycle sprocket inaccordance with a fifth embodiment;

FIG. 15 is an enlarged elevational view of a bicycle sprocket inaccordance with a sixth embodiment;

FIG. 16 is an enlarged elevational view of the bicycle sprocket inaccordance with the sixth embodiment;

FIG. 17 is an elevational view of a bicycle sprocket in accordance witha seventh embodiment;

FIG. 18 is an enlarged elevational view of a bicycle sprocket inaccordance with an eighth embodiment;

FIG. 19 is a cross-sectional view of the bicycle sprocket taken alongline XIX-XIX of FIG. 18;

FIG. 20 is a cross-sectional view of the bicycle sprocket taken alongline XX-XX of FIG. 18;

FIG. 21 is an enlarged elevational view of a bicycle sprocket inaccordance with a ninth embodiment;

FIG. 22 is a cross-sectional view of the bicycle sprocket taken alongline XXII-XXII of FIG. 21;

FIG. 23 is a cross-sectional view of the bicycle sprocket taken alongline XXIII-XXIII of FIG. 21;

FIG. 24 is an elevational view of a bicycle sprocket in accordance witha tenth embodiment; and

FIG. 25 is an enlarged elevational view of a bicycle sprocket inaccordance with an eleventh embodiment for explaining positionalrelationship between the bicycle sprocket and a bicycle chain.

DESCRIPTION OF THE EMBODIMENTS

The embodiments will now be described with reference to the accompanyingdrawings, wherein like reference numerals designate corresponding oridentical elements throughout the various drawings.

First Embodiment

Referring initially to FIG. 1, a bicycle sprocket 10 in accordance witha first embodiment is configured to engage with a bicycle chain 1. Thebicycle sprocket 10 is rotatable about a rotational center axis A. Inthe illustrated embodiment, the bicycle sprocket 10 is a front sprocketconfigured to be provided on a gear crank (right crank) of a bicycle.Structures of the bicycle sprocket 10 can, however, be applied to a rearsprocket.

The bicycle sprocket 10 is configured to be fastened to crank connectingarms 2 a of a sprocket mounting member 2 by bolts (not shown). Thesprocket mounting member 2 is fastened on a crank arm 4 to be rotatableintegrally with the crank arm 4 about the rotational center axis A. Thesprocket mounting member 2 can also be integrally provided with thecrank arm 4 as a single unitary member. Namely, the bicycle sprocket 10is configured to be rotatable integrally with the sprocket mountingmember 2 and the crank arm 4 about the rotational center axis A. Thebicycle sprocket 10 is configured to be rotated about the rotationalcenter axis A in a rotational driving direction D11 during the pedaling.The rotational driving direction D11 is defined along a circumferentialdirection D1 of the bicycle sprocket 10. A direction D12 is definedalong the circumferential direction D1. The direction D12 is opposite tothe rotational driving direction D11.

As seen in FIG. 1, the bicycle sprocket 10 comprises sprocket teeth 12.The sprocket teeth 12 include at least one first tooth 14 and at leastone second tooth 16. In the illustrated embodiment, the sprocket teeth12 include a plurality of first teeth 14 as the at least one first tooth14 and a plurality of second teeth 16 as the at least one second tooth16. The at least one first tooth 14 and the at least one second tooth 16are alternately arranged in the circumferential direction D1 of thebicycle sprocket 10. In the illustrated embodiment, the first teeth 14and the second teeth 16 are alternately arranged in the circumferentialdirection D1. The sprocket teeth 12 can include at least one first tooth14 (e.g., one first tooth 14) and at least one second tooth 16 (e.g.,one second tooth 16) if needed and/or desired. Furthermore, the sprocketteeth 12 can include teeth having a shape different from a shape of eachof the first tooth 14 and the second tooth 16.

The bicycle sprocket 10 further comprises a sprocket body 18 having anannular shape. The sprocket teeth 12 radially outwardly protrude fromthe sprocket body 18. The at least one first tooth 14 and the at leastone second tooth 16 are alternately arranged on a whole circumference ofthe sprocket body 18 in the circumferential direction D1. The sprocketbody 18 is configured to be fastened to the crank connecting arms 2 a ofthe sprocket mounting member 2 by bolts (not shown). In the illustratedembodiment, the sprocket teeth 12 and the sprocket body 18 comprise ametallic material such as aluminum, iron and titanium. The sprocketteeth 12 are integrally provided with the sprocket body 18 as a singleunitary member. The sprocket teeth 12 can, however, be separatelyprovided from the sprocket body 18.

As seen in FIG. 2, the at least one second tooth 16 is adjacent to thefirst tooth 14 and is disposed on a downstream side in the rotationaldriving direction D11 of the bicycle sprocket 10. The sprocket teeth 12include tooth bottoms 12 a defining a root circle RC of the bicyclesprocket 10.

As seen in FIGS. 2 and 3, the at least one first tooth 14 has a firstradial-tooth height H1. The at least one second tooth 16 has a secondradial-tooth height H2. The first radial-tooth height H1 is greater thanthe second radial-tooth height H2. In the illustrated embodiment, thefirst radial-tooth height H1 is defined between the root circle RC and aradially outer end of the first tooth 14. The second radial-tooth heightH2 is defined between the root circle RC and a radially outer end of thesecond tooth 16.

As seen in FIG. 4, the at least one first tooth 14 is configured toengage with outer link plates 1 d of the bicycle chain 1. The at leastone first tooth 14 has a first chain-engaging axial width W1 which issmaller than a first distance L1 defined between opposed outer linkplates 1 d of the bicycle chain 1 and which is larger than a seconddistance L2 defined between opposed inner link plates 1 c of the bicyclechain 1. The at least one second tooth 16 is configured to engage withinner link plates 1 c of the bicycle chain 1. The at least one secondtooth 16 has a second chain-engaging axial width W2 which is smallerthan the second distance L2. Preferably, the first chain-engaging axialwidth W1 is defined so that the at least one first tooth 14 fitlyengages with the outer link plate 1 d, and the second chain-engagingaxial width W2 is defined so that the at least one second tooth 16 fitlyengages with the inner link plates 1 c.

As seen in FIG. 4, the opposed outer link plates 1 d includes opposedinner surfaces if defining an axial space AS1 in which the first tooth14 is to be disposed. The opposed inner link plates 1 c include opposedinner surfaces 1 e defining an axial space AS2 in which the second tooth16 is to be disposed. The first distance L1 is an axial distance betweenthe opposed inner surfaces 1 f of the opposed outer link plates 1 d in adirection D2 parallel to center axes CA of pins 1 b which rotatablysupport rollers 1 a. The second distance L2 is an axial distance betweenthe opposed inner surfaces 1 e of the opposed inner link plates 1 c inthe direction D2 parallel to the center axes CA of the pins 1 b.

As seen in FIG. 5, the first tooth 14 has a first chain-engaging surface14 b and a second chain-engaging surface 14 c. The first chain-engagingsurface 14 b and the second chain-engaging surface 14 c face in an axialdirection D3 parallel to the rotational axis A of the bicycle sprocket10. The first chain-engaging surface 14 b and the second chain-engagingsurface 14 c are contactable with the opposed inner surfaces if of theouter link plates 1 d, respectively. For example, the firstchain-engaging axial width W1 is a maximum axial width defined betweenthe first chain-engaging surface 14 b and the second chain-engagingsurface 14 c in the axial direction D3. In a state where the bicyclechain 1 engages with the bicycle sprocket 10, the axial direction D3coincides with the direction D2 defined with respect to the bicyclechain 1.

As seen in FIG. 6, the second tooth 16 has a third chain-engagingsurface 16 b and a fourth chain-engaging surface 16 c. The thirdchain-engaging surface 16 b and the fourth chain-engaging surface 16 cface in the axial direction D3. The third chain-engaging surface 16 band the fourth chain-engaging surface 16 c are contactable with theopposed inner surfaces 1 e of the inner link plates 1 c, respectively.For example, the second chain-engaging axial width W2 is a maximum axialwidth defined between the third chain-engaging surface 16 b and thefourth chain-engaging surface 16 c in the axial direction D3.

With the bicycle sprocket 10, as seen in FIG. 4, the at least one firsttooth 14 has the first chain-engaging axial width W1 which is smallerthan the first distance L1 defined between opposed outer link plates ofthe bicycle chain 1 and which is larger than the second distance L2defined between opposed inner link plates of the bicycle chain 1. Thisimproves holding function of the bicycle sprocket 10 for the bicyclechain 1.

Furthermore, since contact between the second tooth 16 and the bicyclechain 1 can reduce contact pressure between the first tooth 14 and thebicycle chain 1, it is possible to reduce wear of the first tooth 14compared with a comparative bicycle sprocket including only the firsttooth 14 without the second tooth 16. Accordingly, it is possible tomaintaining the service life of the bicycle sprocket 10 with improvingthe holding function of the bicycle sprocket 10 for the bicycle chain 1.

Second Embodiment

A bicycle sprocket 210 in accordance with a second embodiment will bedescribed below referring to FIGS. 8 and 9. The bicycle sprocket 210 hasthe same configuration as the bicycle sprocket 10 except for thesprocket teeth 12. Thus, elements having substantially the same functionas those in the first embodiment will be numbered the same here, andwill not be described again in detail here for the sake of brevity

As seen in FIGS. 8 and 9, the at least one first tooth 14 includes achamfered part configured to reduce interference between the at leastone first tooth 14 and one of inner ink plates of the bicycle chain 1.In the illustrated embodiment, the first tooth 14 includes chamferedparts 222 configured to reduce interference between one of the innerlink plates 1 c (FIG. 9) of the bicycle chain 1 and the first tooth 14in a state where the first tooth 14 engages with the bicycle chain 1.More specifically, each of the sprocket teeth 12 includes chamferedparts 222 configured to reduce interference between each of the sprocketteeth 12 and one of the inner link plates 1 c (FIG. 9) of the bicyclechain 1 in a state where the sprocket teeth 12 engage with the bicyclechain 1.

As seen in FIG. 8, the chamfered part 222 of the first tooth 14 isadjacent to the tooth bottom 12 a of the first tooth 14. In theillustrated embodiment, the chamfered part 222 of the first tooth 14 isadjacent to a first tooth bottom 14 a of the first tooth 14. Thechamfered part 222 of the first tooth 14 preferably extends from thefirst tooth bottom 14 a to an end of the first tooth 14.

With the bicycle sprocket 210, the chamfered part 222 can reduce wear ofthe first tooth 14 in addition to the advantageous effect obtained bythe bicycle sprocket 10 in accordance with the first embodiment.

Third Embodiment

A bicycle sprocket 310 in accordance with a third embodiment will bedescribed below referring to FIGS. 10 to 12. The bicycle sprocket 310has the same configuration as the bicycle sprocket 10 except forsprocket teeth 12. Thus, elements having substantially the same functionas those in the first embodiment will be numbered the same here, andwill not be described again in detail here for the sake of brevity.

As seen in FIGS. 10 to 12, the bicycle sprocket 10 further comprises atleast one additional tooth having a chain-engaging axial width smallerthan the second distance L2 defined between opposed inner link plates 1c of the bicycle chain 1. Each of the at least one additional tooth isdisposed adjacent to the at least one first tooth 14 such that thebicycle chain 1 is shifted between the bicycle sprocket 10 and anadditional bicycle sprocket in an area in which the at least oneadditional tooth is positioned.

In the illustrated embodiment, the bicycle sprocket 310 furthercomprises an additional tooth 317. The additional tooth 317 is disposedbetween adjacent two of the first teeth 14 such that the bicycle chain 1is shifted between the bicycle sprocket 10 and an additional bicyclesprocket 350 (FIG. 12) in an area in which the additional tooth 317 ispositioned. The additional bicycle sprocket 350 is rotatable integrallywith the bicycle sprocket 310. The structures of the bicycle sprocket310 can be applied to the additional bicycle sprocket 350 if neededand/or desired.

As seen in FIG. 10, the additional tooth 317 has a third radial-toothheight H3. The third radial-tooth height H3 is larger than the secondradial-tooth height H2 of the second tooth 16. The third radial-toothheight H3 is substantially equal to the first radial-tooth height H1 ofthe first tooth 14.

As seen in FIG. 11, the additional tooth 317 has a chain-engaging axialwidth W3 which is smaller than the second distance L2. Thechain-engaging axial width W3 is smaller than the first chain-engagingaxial width W1 of the first tooth 14. The chain-engaging axial width W3is substantially equal to the second chain-engaging axial width W2 ofthe second tooth 16.

As seen in FIG. 12, the additional tooth 317 has a first chain-engagingsurface 317 b and a second chain-engaging surface 317 c. The firstchain-engaging surface 317 b and the second chain-engaging surface 317 cface in the axial direction D3. The first chain-engaging surface 317 band the second chain-engaging surface 317 c are contactable with theopposed inner surfaces 1 e of the inner link plates 1 c, respectively.For example, the chain-engaging axial width W3 is a maximum axial widthdefined between the first chain-engaging surface 317 b and the secondchain-engaging surface 317 c in the axial direction D3 parallel to therotational axis A of the bicycle sprocket 310.

As seen in FIG. 12, the bicycle sprocket 310 may further comprise aspike pin 352 configured to guide the bicycle chain 1 toward thesprocket teeth 12 (FIG. 10) during shifting operation. The bicyclesprocket 310 can include a plurality of spike pins as the spike pin 352.The spike pin 352 is made of a metallic material and is a separatemember from the sprocket teeth 12 and the sprocket body 18. The spikepin 352 can, however, be integrally provided with the sprocket teeth 12and the sprocket body 18.

As described above, the bicycle sprocket 10 in accordance with the firstembodiment can be applied to a bicycle sprocket assembly for shiftinggears.

Fourth Embodiment

A bicycle sprocket 410 in accordance with a fourth embodiment will bedescribed below referring to FIG. 13. The bicycle sprocket 410 has thesame configuration as the bicycle sprocket 10 except for the sprocketteeth 12. Thus, elements having substantially the same function as thosein the first embodiment will be numbered the same here, and will not bedescribed again in detail here for the sake of brevity.

As seen in FIG. 13, each of the sprocket teeth 12 has a multi-layeredstructure with different materials. Each of the sprocket teeth 12includes a first sprocket layer 430, a second sprocket layer 432, and athird sprocket layer 434. For example, the first sprocket layer 430 ismade of a first-layer material comprising iron. The second sprocketlayer 432 can be made of a second-layer material comprising a resinmaterial. The third sprocket layer 434 is made of a third-layer materialcomprising iron. The second sprocket layer 432 is provided between thefirst sprocket layer 430 and the third sprocket layer 434. For example,the first sprocket layer 430 and the third sprocket layer 434 are bondedto the second sprocket layer 432 by integral molding.

Materials of the multi-layered structure of the sprocket teeth 12 arenot limited to the above embodiment. For example, the second sprocketlayer 432 can be made of a second-layer material comprising aluminum. Insuch embodiment, the second sprocket layer 432 is bonded to the firstsprocket layer 430 and the third sprocket layer 434 using diffusionbonding or bonding material such as adhesive.

With the bicycle sprocket 410, the multi-layered structure can saveweight of the sprocket teeth 12 in addition to the advantageous effectobtained by the bicycle sprocket 10 in accordance with the firstembodiment.

Fifth Embodiment

A bicycle sprocket 510 in accordance with a fifth embodiment will bedescribed below referring to FIG. 14. The bicycle sprocket 510 has thesame configuration as the bicycle sprocket 10 except for the sprocketteeth 12. Thus, elements having substantially the same function as thosein the first embodiment will be numbered the same here, and will not bedescribed again in detail here for the sake of brevity.

As seen in FIG. 14, each of the sprocket teeth 12 includes the toothbottom 12 a defining the root circle RC of the bicycle sprocket 510. Atleast one of the sprocket teeth 12 includes a closed opening at leastpartially provided radially outward of the root circle RC. In theillustrated embodiment, each of the first teeth 14 includes a closedopening 513 at least partially provided radially outward of the rootcircle RC. Each of the second teeth 16 includes a closed opening 515entirely provided radially outward of the root circle RC. The closedopening such as the closed openings 513 and 515 can be provided in atleast one of the sprocket teeth 12 if needed and/or desired. The closedopening 513 can be entirely provided radially outward of the root circleRC if needed and/or desired. Furthermore, the closed opening 515 can beat least partially provided radially outward of the root circle RC ifneeded and/or desired. One of the closed openings 513 and 515 can beomitted from the bicycle sprocket 510 if needed and/or desired.

With the bicycle sprocket 510, the closed openings 513 and 515 can saveweight of the sprocket teeth 12 in addition to the advantageous effectobtained by the bicycle sprocket 10 in accordance with the firstembodiment.

Sixth Embodiment

A bicycle sprocket 610 in accordance with a sixth embodiment will bedescribed below referring to FIGS. 15 and 16. The bicycle sprocket 610has the same configuration as the bicycle sprocket 10 except for thesprocket teeth 12. Thus, elements having substantially the same functionas those in the first embodiment will be numbered the same here, andwill not be described again in detail here for the sake of brevity.

As seen in FIGS. 15 and 16, at least one of the sprocket teeth 12includes a cutout configured to increase flexibility of the at least oneof the sprocket teeth 12. In the illustrated embodiment, as seen in FIG.15, each of the first teeth 14 includes a cutout 617 configured toincrease flexibility of each of the first teeth 14. The cutout 617extends in the circumferential direction D1. More specifically, thecutout 617 extends in the rotational driving direction D11 from one ofthe tooth bottoms 12 a toward the other of the tooth bottoms 12 a in thefirst tooth 14.

Similarly, as seen in FIG. 16, each of the second teeth 16 includes acutout 619 configured to increase flexibility of each of the secondteeth 16. The cutout 619 extends in the circumferential direction D1.More specifically, the cutout 619 extends in the rotational drivingdirection D11 from one of the tooth bottoms 12 a toward the other of thetooth bottoms 12 a in the second tooth 16. The cutout such as thecutouts 617 and 619 can be provided in at least one of the sprocketteeth 12 if needed and/or desired. The shapes of the cutouts 617 and 619are not limited to the illustrated embodiment.

With the bicycle sprocket 610, the cutout 617 allows the first tooth 14to absorb a shock caused by the first tooth 14 and the bicycle chain 1,and thereby it is possible to improve wear resistance of the first tooth14, in addition to the advantageous effect obtained by the bicyclesprocket 10 in accordance with the first embodiment. Similarly, thecutout 619 allows the second tooth 16 to absorb a shock caused by thesecond tooth 16 and the bicycle chain 1, and thereby it is possible toimprove wear resistance of the second tooth 16, in addition to theadvantageous effect obtained by the bicycle sprocket 10 in accordancewith the first embodiment.

Seventh Embodiment

A bicycle sprocket 710 in accordance with a seventh embodiment will bedescribed below referring to FIG. 17. The bicycle sprocket 710 has thesame configuration as the bicycle sprocket 10 except for the sprocketteeth 12 and the sprocket body 18. Thus, elements having substantiallythe same function as those in the first embodiment will be numbered thesame here, and will not be described again in detail here for the sakeof brevity.

As seen in FIG. 17, the bicycle sprocket 710 comprises sprocket teeth712. The sprocket teeth 712 include at least one first tooth 714 and atleast one second tooth 716. In the illustrated embodiment, the sprocketteeth 712 include a plurality of first teeth 714 as the at least onefirst tooth 714 and a plurality of second teeth 716 as the at least onesecond tooth 716. The at least one first tooth 714 and the at least onesecond tooth 716 are alternately arranged in the circumferentialdirection D1 of the bicycle sprocket 10.

The bicycle sprocket 710 further comprises a sprocket body 718 having anannular shape. The sprocket teeth 712 are separate members from eachother and are spaced apart from each other in the circumferentialdirection D1 of the bicycle sprocket 710. The sprocket body 718 isconfigured to be fastened to the crank connecting arms 2 a of thesprocket mounting member 2 by bolts (not shown).

Each of the sprocket teeth 712 includes a base part and a tooth part. Inthe illustrated embodiment, the first tooth 714 includes a base part 714a and a tooth part 714 b. The base part 714 a is implanted in thesprocket body 718. The tooth part 714 b radially outwardly protrudesfrom the base part 714 a. Similarly, the second tooth 716 includes abase part 716 a and a tooth part 716 b. The base part 716 a is implantedin the sprocket body 718. The tooth part 716 b radially outwardlyprotrudes from the base part 716 a.

Each of the sprocket teeth 712 is made of a first material comprising ametallic material e.g. which can be selected from a group comprisingaluminum, titanium or iron. The sprocket body 718 is made of a secondmaterial which is lighter than the first material. For example, such asecond material can be selected from a group comprising aluminum,titanium and a resin material. The first teeth 714 and the second teeth716 are at least partially embedded in the sprocket body 718 by integralmolding such as insertion molding.

With the bicycle sprocket 710, since the sprocket body 718 is made ofthe second material comprising a resin material, it is possible to saveweight of the bicycle sprocket 710 in addition to the advantageouseffect obtained by the bicycle sprocket 10 in accordance with the firstembodiment.

Eighth Embodiment

A bicycle sprocket 810 in accordance with an eighth embodiment will bedescribed below referring to FIGS. 18 to 20. The bicycle sprocket 810has the same configuration as the bicycle sprocket 10 except for thesprocket teeth 12. Thus, elements having substantially the same functionas those in the first embodiment will be numbered the same here, andwill not be described again in detail here for the sake of brevity.

As seen in FIG. 18, the sprocket teeth 12 are equally spaced apart fromeach other in the circumferential direction D1 of the bicycle sprocket810. Each of the sprocket teeth 12 has a center line radially extendingfrom the rotational axis A of the bicycle sprocket 810. Each of thesprocket teeth 12 has a symmetrical shape with respect to the centerline.

In the illustrated embodiment, each of the first teeth 14 has a centerline CL1 radially extending from the rotational axis A of the bicyclesprocket 810. Each of the first teeth 14 has a symmetrical shape withrespect to the center line CL1. More specifically, each of the firstteeth 14 has a symmetrical shape with respect to the center line CL1when viewed from a direction of the rotational axis A.

As seen in FIG. 19, the center line CL1 is perpendicular to therotational axis A. Each of the first teeth 14 has a symmetrical shapewith respect to the center line CL1 when viewed from the circumferentialdirection D1 of the bicycle sprocket 810.

Similarly, as seen in FIG. 18, each of the second tooth 16 has a centerline CL2 radially extending from the rotational axis A of the bicyclesprocket 810. Each of the second teeth 16 has a symmetrical shape withrespect to the center line CL2. More specifically, each of the secondteeth 16 has a symmetrical shape with respect to the center line CL2when viewed from the direction of the rotational axis A.

As seen in FIG. 20, the center line CL2 is perpendicular to therotational axis A. Each of the second teeth 16 has a symmetrical shapewith respect to the center line CL2 when viewed from the circumferentialdirection D1 of the bicycle sprocket 810.

With the bicycle sprocket 810, since each of the sprocket teeth 12 has asymmetrical shape with respect to the center line CL1 or CL2, bothcircumferential sides of the sprocket tooth 12 can be used as a drivingside configured to face in the rotational driving direction D11. Thisallows the bicycle sprocket 810 to be used as a both-side usablesprocket in addition to the advantageous effect obtained by the bicyclesprocket 10 in accordance with the first embodiment.

Ninth Embodiment

A bicycle sprocket 910 in accordance with a ninth embodiment will bedescribed below referring to FIGS. 21 to 23. The bicycle sprocket 910has the same configuration as the bicycle sprocket 10 except for thesprocket teeth 12. Thus, elements having substantially the same functionas those in the first embodiment will be numbered the same here, andwill not be described again in detail here for the sake of brevity.

As seen in FIGS. 21 and 22, in the bicycle sprocket 910, the at leastone first tooth 14 includes a first radial contact part 960 configuredto contact at least one of intermediate portions 1 g of outer linkplates 1 d of the bicycle chain 1 in a radial direction D4 (FIG. 22) ofthe bicycle sprocket 910 in a state where the at least one first tooth14 engages with the outer link plates 1 d of the bicycle chain 1. Thefirst tooth 14 includes a first tooth body 962 radially outwardlyprotruding from the first radial contact part 960. The first radialcontact part 960 is closer to the tooth bottoms 12 a than the firsttooth body 962. A radially outer surface 960 a of the first radialcontact part 960 has a shape complementary with an outer shape of theintermediate portion 1 g of the outer link plate 1 d. More specifically,the radially outer surface 960 a of the first radial contact part 960has a curved shape and is provided along an edge of the intermediateportion 1 g of the outer link plate 1 d.

As seen in FIG. 22, the first tooth body 962 has the firstchain-engaging axial width W1. The first tooth body 962 includes thefirst chain-engaging surface 14 b and the second chain-engaging surface14 c. The first radial contact part 960 has a first axial width W41larger than the first distance L1 defined between opposed outer linkplates 1 d of the bicycle chain 1. The first axial width W41 is largerthan the first chain-engaging axial width W1.

As seen in FIG. 22, the first radial contact part 960 protrudes from thefirst chain-engaging surface 14 b and the second chain-engaging surface14 c in the axial direction D3. The first radial contact part 960 can,however, protrude from at least one of the first chain-engaging surface14 b and the second chain-engaging surface 14 c.

As seen in FIGS. 21 and 23, the at least one second tooth 16 includes asecond radial contact part 964 configured to contact at least one ofintermediate portions 1 h of inner link plates 1 c of the bicycle chain1 in the radial direction D4 (FIG. 23) of the bicycle sprocket 10 in astate where the at least one second tooth 16 engages with the inner linkplates 1 c of the bicycle chain 1. The second tooth 16 includes a secondtooth body 966 radially outwardly protruding from the second radialcontact part 964. The second radial contact part 964 is closer to thetooth bottoms 12 a than the second tooth body 966. A radially outersurface 964 a of the second radial contact part 964 has a shapecomplementary with an outer shape of the intermediate portion 1 h of theinner link plate 1 c. More specifically, the radially outer surface 964a of the second radial contact part 964 has a curved shape and isprovided along an edge of the intermediate portion 1 h of the inner linkplate 1 c.

As seen in FIG. 23, the second tooth body 966 has the secondchain-engaging axial width W2. The second tooth body 966 includes thethird chain-engaging surface 16 b and the fourth chain-engaging surface16 c. The second radial contact part 964 has a second axial width W42larger than the second distance L2 defined between opposed inner linkplates 1 c of the bicycle chain 1. The second axial width W42 is largerthan the second chain-engaging axial width W2.

As seen in FIG. 23, the second radial contact part 964 protrudes fromthe third chain-engaging surface 16 b and the fourth chain-engagingsurface 16 c in the axial direction D3. The second radial contact part964 can, however, protrude from at least one of the third chain-engagingsurface 16 b and the fourth chain-engaging surface 16 c.

With the bicycle sprocket 910, the first radial contact part 960 isconfigured to contact the intermediate portions 1 g of the outer linkplates 1 d of the bicycle chain 1 in the radial direction D4.Accordingly, the first radial contact part 960 can improve stability ofthe outer link plates 1 d engaging with the first tooth 14 in additionto the advantageous effect obtained by the bicycle sprocket 10 inaccordance with the first embodiment.

Similarly, the second radial contact part 964 is configured to contactthe intermediate portions 1 h of the inner link plates 1 c of thebicycle chain 1 in the radial direction D4. Accordingly, the secondradial contact part 964 can improve stability of the inner link plates 1c engaging with the second tooth 16 in addition to the advantageouseffect obtained by the bicycle sprocket 10 in accordance with the firstembodiment.

Tenth Embodiment

A bicycle sprocket 1010 in accordance with a tenth embodiment will bedescribed below referring to FIG. 24. The bicycle sprocket 1010 has thesame configuration as the bicycle sprocket 10 except for the sprocketbody 18. Thus, elements having substantially the same function as thosein the first embodiment will be numbered the same here, and will not bedescribed again in detail here for the sake of brevity.

As seen in FIG. 24, the bicycle sprocket 1010 comprises the sprocketteeth 12. The bicycle sprocket 1010 further comprises a sprocket body1018 having an annular shape. Each of the sprocket teeth 12 is made of afirst material comprising a metallic material. The sprocket body 1018 ismade of a second material comprising a resin material. The bicyclesprocket 1010 further comprises a ring portion 1019 having an annularshape. The sprocket teeth 12 protrude radially outward from the ringportion 1019. For example, the ring portion 1019 is made of the firstmaterial. The sprocket teeth 12 are integrally provided with the ringportion 1019 as a single unitary member. The ring portion 1019 is atleast partially embedded in the sprocket body 1018. For example, thering portion 1019 is embedded in the sprocket body 1018 by integralmolding such as insertion molding. The sprocket body 1018 is configuredto be fastened to the crank connecting arms 2 a of the sprocket mountingmember 2 by bolts (not shown).

With the bicycle sprocket 1010, it is possible to save weight of thebicycle sprocket 1010 in addition to the advantageous effect obtained bythe bicycle sprocket 10 in accordance with the first embodiment.

Eleventh Embodiment

A bicycle sprocket 1110 in accordance with an eleventh embodiment willbe described below referring to FIG. 25. The bicycle sprocket 1110 hasthe same configuration as the bicycle sprocket 10 except for the secondteeth 16. Thus, elements having substantially the same function as thosein the first embodiment will be numbered the same here, and will not bedescribed again in detail here for the sake of brevity.

As seen in FIG. 25, the sprocket teeth 12 of the bicycle sprocket 1110includes the at least one first tooth 14 and at least one second tooth1116. In the illustrated embodiment, the sprocket teeth 12 include theplurality of first teeth 14 as the at least one first tooth 14 andplurality of second teeth 1116 as the at least one second tooth 1116.The first teeth 14 and the second teeth 1116 are alternately arranged inthe circumferential direction D1.

The at least one second tooth 1116 is adjacent to the first tooth 14 anddisposed on a downstream side in the rotational driving direction D11 ofthe bicycle sprocket 1110. In the illustrated embodiment, the secondtooth 1116A is adjacent to the first tooth 14A and disposed on adownstream side with respect to the first tooth 14A in the rotationaldriving direction D11 of the bicycle sprocket 1110.

The at least one second tooth 1116 is configured to engage with theinner link plates 1 c of the bicycle chain 1. The at least one secondtooth 1116 has a second radial-tooth height H112. The first radial-toothheight H1 is greater than the second radial-tooth height H112. In theillustrated embodiment, the second radial-tooth height H112 of thesecond teeth 1116 is less than the second radial-tooth height H2 of thesecond teeth 16 in accordance with the first embodiment.

As seen in FIG. 25, the at least one first tooth 14 is configured toengage with the bicycle chain 1 before the second tooth 1116 engageswith the bicycle chain 1. For example, the first tooth 14A engages withthe bicycle chain 1 (the outer link plates 1 d) before the second tooth1116A engages with the bicycle chain 1 (the inner link plates 1 c) sincethe first radial-tooth height H1 of the first tooth 14A is greater thanthe second radial-tooth height H112 of the second tooth 1116A.

With the bicycle sprocket 1110, it is possible to obtain the sameadvantageous effect as that of the bicycle sprocket 10 in accordancewith the first embodiment.

In the above embodiments, the term “attached” or “attaching”, as usedherein, encompasses configurations in which an element directly attachedto another element by affixing the element is directly to the otherelement; configurations in which the element is indirectly attached tothe other element via the intermediate member(s); and configurations inwhich one element is integral with another element, i.e. one element isessentially part of the other element. This concept also applies towords of similar meaning, for example, “joined”, “connected”, “coupled”,“mounted”, “fixed” and their derivatives except for the terms “bonded”and “bonding.”

The term “comprising” and its derivatives, as used herein, are intendedto be open ended terms that specify the presence of the stated features,elements, components, groups, integers, and/or steps, but do not excludethe presence of other unstated features, elements, components, groups,integers and/or steps. This concept also is applied to words of similarmeaning, for example, the terms “have”, “include” and their derivatives.

The terms “member”, “section”, “portion”, “part” or “element” when usedin the singular can have the dual meaning of a single part or aplurality of parts.

The ordinal numbers such as the terms “first” or “second” recited in thepresent application are merely identifiers, but do not have any othermeanings, for example, a particular order and the like. Moreover, forexample, the term “first element” itself does not imply an existence of“second element”, and the term “second element” itself does not imply anexistence of “first element.”

Finally, terms of degree such as “substantially”, “about” and“approximately” as used herein mean a reasonable amount of deviation ofthe modified term such that the end result is not significantly changed.

Obviously, numerous modifications and variations of the presentinvention are possible in light of the above teachings. It is thereforeto be understood that within the scope of the appended claims, theinvention may be practiced otherwise than as specifically describedherein.

What is claimed is:
 1. A bicycle sprocket having a rotational centeraxis, the bicycle sprocket comprising: sprocket teeth including at leastone first tooth configured to engage with outer link plates of a bicyclechain and having a first radial-tooth height, the at least one firsttooth having a first chain-engaging axial width which is smaller than afirst distance defined between opposed outer link plates of the bicyclechain and which is larger than a second distance defined between opposedinner link plates of the bicycle chain, the at least one first toothhaving an axial center plane perpendicular to the rotational centeraxis, the axial center plane of the at least one first tooth beingprovided at an axial center of the at least one first tooth in an axialdirection parallel to the rotational center axis, and at least onesecond tooth adjacent to the first tooth and disposed on a downstreamside in a rotational driving direction of the bicycle sprocket, the atleast one second tooth being configured to engage with inner link platesof the bicycle chain, the at least one second tooth having a secondradial-tooth height, the first radial-tooth height being greater thanthe second radial-tooth height, the at least one first tooth including atooth tip having an axial center plane perpendicular to the rotationalcenter axis, the axial center plane of the tooth tip being provided atan axial center of the tooth tip in the axial direction, the tooth tiphaving a rectangular shape longitudinally extending in a circumferentialdirection of the bicycle sprocket, and the axial center plane of thetooth tip being offset from the axial center plane of the at least onefirst tooth in the axial direction.
 2. The bicycle sprocket according toclaim 1, wherein the sprocket teeth include a plurality of first teethas the at least one first tooth, and a plurality of second teeth as theat least one second tooth.
 3. The bicycle sprocket according to claim 1,wherein the at least one first tooth and the at least one second toothare alternatively arranged in the circumferential direction of thebicycle sprocket.
 4. The bicycle sprocket according to claim 1, furthercomprising: a sprocket body having a circular shape.
 5. The bicyclesprocket according to claim 4, wherein the at least one first tooth andthe at least one second tooth are alternatively arranged on a wholecircumference of the sprocket body in the circumferential direction. 6.The bicycle sprocket according to claim 4, wherein the sprocket teethare integrally provided with the sprocket body as a single unitarymember.
 7. The bicycle sprocket according to claim 1, wherein the atleast one second tooth has a second chain-engaging axial width which issmaller than the second distance.